Rged arc furnace method for the introduction of hydrocarbon oilsinto an electric subme

ABSTRACT

A METHOD FOR THE INTRODUCTION OF HYDROCARBON OILS TO THE HOT ZONES OF A SUBMERGTED ARC REDUCTION FURNACE THROUGH A SUBSTANTIALLY VERTICAL CANAL IN THE ELECTRODE. THE OIL IS MIXED WITH DISINTEGRATED SOLID REACTANTS TO BE USED IN THE METALLURGICAL PROCESS OF THE FURNACE. THE MIXTURE OBTAINED IS FED THROUGH A CONDUIT WHICH AT LEAST WITH ITS LOWER END PROJECTS INTO THE VERTICAL CANAL. THE LOWER END OPENING OF THE CONDUIT IS SUBSTANTIALLY SMALLER THAN THE CROSS SECTION OF THE CANAL. THE MIXTURE IS ALLOWED TO FALL FROM THE LOWER END OF THE CONDUIT TO REACH THE INTERIOR OF THE FURNACE AFTER A FREE FALL THROUGH THE CANAL, AND A GAS BLOWS DOWNWARD THROUGH THE CANAL. A HOLLOW ELECTRODE IS USED HAVING A FEED SPOUT PROVIDED CENTRALLY WITHIN THE VERTICAL CANAL AND ABOVE THE HIGH TEMEPERATURE REGION OF THE ELECTRODE, THE OUTLET OPENING   OF THE SPOUT BEING SUBSTANTIALLY SMALLER THAN THE CROSS SECTION OF THE CANAL OF THE ELECTRODE, AND A CONDUIT CONNECTS THE SPOUT WITH A SOURCE OF THE MATERIAL TO BE FED THROUGH THE SPOUT.

Sept. 18,1973 E. FALKUM L 3,759,696

METHOD FOR THE lNTRODUCTION OF HYDROCARBON OILS INTO AN ELECTRIC .SUBMERGED ARC FURNACE Filed Aug. 11, 1969 {mm/2 flu mm 1M2 Fi i/WED P5 5; MMMMWZQZL United States Patent 3,759,696 METHOD FOR THE INTRODUCTION OF HYDRO- CARBON OILS INTO AN ELECTRIC SUBMERGED ARC FURNACE Einar Falkum, Porsgrunn, and Ivar Brunborg Oslo, Norway, assignors to Norsk Hydro-Elektrisk Kvaelstofaktieselskab, Oslo, Norway Filed Aug. 11, 1969, Ser. No. 849,045 Int. Cl. CZlc 5/52; CZZd 7/00; H051) 7/06 US. C]. 7511 6 Claims ABSTRACT OF THE DISCLOSURE A method for the introduction of hydrocarbon oils to the hot zones of a submerged arc reduction furnace through a substantially vertical canal in the electrode. The oil is mixed with disintegrated solid reactants to be used in the metallurgical process of the furnace. The mixture obtained is fed through a conduit which at least with its lower end projects into the vertical canal. The lower end opening of the conduit is substantially smaller than the cross section of the canal. The mixture is allowed to fall from the lower end of the conduit to reach the interior of the furnace after a free fall through the canal, and a gas blows downward through the canal. A hollow electrode is used having a feed spout provided centrally within the vertical canal and above the high temperature region of the electrode, the outlet opening of the spout being substantially smaller than the cross section of the canal of the electrode, and a conduit connects the spout with a source of the material to be fed through the spout.

The invention relates to a method for the introduction of hydrocarbon oils into an electric submerged arc furnace, and more particularly to a method of introducing the oils into such furnace through a hollow vertical electrode. The invention further relates to means for carrying out said method.

In the electrothermal reduction of ores and in the production of calcium carbide, the reducing agent is usually coke. As is well known, it may sometimes be desirable, for better economy, to substitute hydrocarbons for coke to some extent. Various methods have been proposed previously for the introduction of hydrocarbons into a furnace through a longitudinal canal in the electrode, including the introduction of oils into the crater of the furnace.

However, such introduction of hydrocarbon oils into the crater of the furnace has turned out to present serious difficulties, and to our knowledge none of the previous proposals has turned out to be satisfactorily useful in practice. A major difficulty is that the canal, through which the oils are fed, soon gets plugged by carbon formed due to cracking of the oil.

According to a previous proposal, the hydrocarbons are introduced through a pipe, which in the case of a self-baking electrode is imbedded in the electrode and is therefore carried downward as the latter is consumed. The pipe, which is usually made of steel, will melt away at the lower end. If a hydrocarbon oil, for instance a heavy fuel oil, is allowed to flow through the pipe, the latter will be plugged after a little while, since the oil will be thermally destructed. Depending on the size of the furnace, the temperature of the electrode and other factors, the plugging of the pipe would occur at some longer or shorter distance from the tip of the electrode, or the pipe may possibly be plugged due to cracking products formed in the crater being deposited on the tip of the electrode to plug the lower end of the canal in the electrode. In all our tests using such conventional introduction, the result was complete plugging after a couple of minutes.

It has been proposed to facilitate the introduction of oils to the crater through a canal in the electrode by cooling the electrode, for instance by circulating water through ducts provided in the electrode. This way of solving the problems entails, however, so many difiiculties and disadvantages, especially when the electrode is of the self-baking or consumable type, that it is quite unsatisfactory.

An object of the invention is to practically avoid the cracking of the oil in the canal of the electrode.

Another object of the invention is to facilitate the removal of any carbonaceous deposits that might occur in the hot zones of the canal.

Other objects and features of the invention will be evident from the description below.

According to the invention, the introduction of hydrocarbon oils to the hot zones of a submerged arc furnace via a vertical canal provided in the electrode thereof is effected by mixing the oil with disintegrated solid re actants to be used in the metallurgical process of the furnace and feeding the mixture through a conduit which at least with its lower end projects into said vertical canal, the lower end opening of said conduit being substantially smaller than the cross section of said canal,

allowing said mixture to fall from the lower end of said conduit to reach the interior of the furnace after a free fall through said canal, and flowing a gas downward through said canal.

The diameter of the end opening of said conduit ought to be less than the half of the inner diameter of said canal. The ratio between said diameters depends on the height of the electrode and the consistency of the material to be fed through the electrode. In some cases the diameter of the end opening of the conduit preferably ought to be about A of the inner diameter of said canal.

Preferably, the mixture of oil and disintegrated solid reactants being fed through said conduit is of a paste-like consistency. To achieve such consistence, disintegrated coke if desired, can be worked into the mixture prior to its introduction through said conduit.

The gas flowed through the canal in the electrode concurrently with the oil-containing mixture, which gas is below called the washing gas, advantageously can be a gas produced by the furnace process. According to the invention, gas components capable of oxidising carbonaceous material at high temperatures are added to the washing gas to the extent necessary to burn away carbonaceous deposits in the canal, to counteract any tendency of such deposits to form and grow. Such oxidis ing components of the washing gas are for instance carbon dioxide or water vapor.

The invention also provides a hollow electrode to be used in a submerged arc reduction furnace, wherein reducing agent is to be charged through a vertical canal provided in the electrode and the hollow electrode is characterized by a feed spout provided centrally within the vertical canal and above the high temperature region of the electrode, the outlet opening of the spout being substantially smaller than the cross section of the canal of the electrode, and a conduit connecting the spout with a source of the material to be fed through the spout. This conduit preferably is a flexible tube, as further explained below.

The diameter of the end opening of said conduit ought to be less than the half of the inner diameter of said canal. The ratio between said diameters depends on the height of the electrode and the consistency of the material to be fed through the electrode. In some cases the diameter of the end opening of the conduit preferably ought to be about /3 of the inner diameter of said canal.

A hollow electrode according to the invention is shown diagrammatically in the drawing, where the electrode is of the self-baking type and has been designated by the numeral 1, while 2 is a mantle, and 3 indicates electrode current contacts. The longitudinal canal of the electrode shown is designated by the numeral 4 and in this case consists of steel piping. This piping as well as the mantle 2 will melt or burn away at their lower ends as the electrode is lowered during operation, and their lower edges have been designated by 4a and 2a, respectively.

The feed conduit is generally designated by '5. This conduit is arranged concentrically in the canal 4 and the annular passage between the conduit 5 and the walls of the canal 4 is closed near the top of the electrode by packing material 6. A supply conduit outside the electrode 1 is indicated by 7, a manometer by 8 and a rotameter by 9. The washing gas is supplied through a conduit 10 provided with a manometer 11.

The conduit 5 as shown is composed of a feed spout 5a and a flexible tubing 5b, connected to the spout 5a by a coupling 50. Means for maintaining the spout 5a in a concentric position with the canal 4 is designated by 5d.

The feed spout 5a is preferably placed above the high temperature zone of the electrode 1. It is thereby achieved that the hydrocarbon oil cannot possibly be heated to cracking temperature while in the conduit 5. Thus, cracking cannot occur before the oil-containing feed has reached a region some distance below the spout 5a, and since the downward velocity of the feed will accelerate, the feed will be exposed to cracking temperatures only during a very short period of time. Further, the washing gas will aid in preventing cracking products, if any should be produced in the canal 4, from being deposited on the walls of the canal 4.

By virtue of the method and the hollow electrode of the invention, cracking of the oil fed through the electrode will be minimised.

Using a flexible tubing 5b connected to the spout 5a, the entire conduit 5 readily be arranged to follow the vertical movements of the electrode 1 during operations. Further, the flexible tubing 5b permits the entire conduit 5 including the spout 5a to be readily pulled out from the canal 4 when desired, for instance when, at intervals, the mantle 2 is to be extended upwardly. This is a con siderable advantage, particularly in the case of a high furnace. Thus, in a 40 MW calcium carbide furnace for instance, the high temperature region of the electrode will extend about 3-4 meters upwards from the tip of the electrode, while the full height of the electrode may be some -20 meters, and it would then be advantageous to place the spout 5a several meters below the top of the electrode.

In the case when the material to be fed through the hollow electrode has a relatively high degree of fluidity, the feed can be pumped by any suitable metering pump. It has been observed, however, that such fluid feed can have a tendency to spread during a free fall, so that more or less of the feed may hit the inner Walls of the canal, depending on the height of the free fall. The result may be cracking of hydrocarbons on the walls of the canal 4 in the high temperature region, and, eventually, plugging of the canal 4. Therefore, according to the invention, the material to be fed via the electrode preferably is to have a thicker, that is a paste-like consistency. Such consistency can be obtained by increasing the proportion of solid constituents in the material. If desired, a portion of the solids may consist of disintegrated coke. The consistency of the feed material also can be modified by using more viscous hydrocarbons. A paste-like consistency means a state between the solid and the liquid state. When feeding such semi-solid mixture it is preferred to use a screw instead of a metering pump.

Following is a brief description of a few experiments carried out under conditions permitting, in partcular, a close study of the abovementioned spreading tendency.

A transparent plastics tube, 11 m. long and having 10 cm. inside diameter was arranged in vertical position to correspond to the canal 4. A short pipe having inside diameter 16 mm. was placed inside the tube concentricaL ly therewith near the upper end of the tube. Thus, this short pipe corresponds to the spout 5a of the drawing.

By means of a feeding screw a pastous mixture of powdered lime, powdered coke and fuel oil was pressed through the short pipe at a rate of 210 kg./hour. The pastous material fell 1011 meters through the plastics tube in form of lumps without coming into contact with the inner walls of the tube.

The same paste mixture was passed through the spout at a rate of 375 kg./hour, and also in this case the paste came out from the spout in the form of lumps to fall through the tube without coming into contact with the inner walls of the tube.

Similar experiments were carried out using varying proportions of oil and solids, and also using varying proportions of powdered coke and lime. Thus, one of the mixtures tried consisted of oil and powdered coke and lime in such proportions as to stoichiometrically correspond to the equation CaO+3C=CaC +CO, the oil and the coke both being sources of carbon.

In all experiments the paste-like material was made to fall freely 10-1l rn. through the plastics tube without coming into contact with the walls of the tube.

According to our observations, a free fall of 10-11 meters can hardly be achieved using an oil-like fiuid or a suspension of a similar fluidity. Although such liquid material when falling vertically from the spout were made to fall freely 7-8 meters through the plastics tube described, without coming into contact with the walls of the tube, it turned out that the risk of obtaining such undesirable contact is, in the long run, considerably greater using a fluid-like feed than when using a paste-like feed.

In addition to the advantages already mentioned in the foregoing, the invention combines the following substantial advantages when the paste-like form of feed is used:

(1) Disintegrated materials generally obtained unavoidably during the preparation and handling of starting materials for the process of a metallurgical furnace, such as fines of coke, lime and ore, can be utilized.

(2) A further disintegration of such fines is not required, since the paste-like material is advantageously fed by means of apparatus in which the grain size is not a critical factor.

(3) It will usually be unnecessary to heat the oil.

(4) All problems due to settling of solids in supply pipes etc. when operations come to a halt for some reason (for instance when the electrode mantle is to be provided with an extension) are avoided.

When the paste-like material of the invention is introduced through the hollow electrode, where the spout 5a is placed above the high temperature region of the electrode, the material can obtain a very high velocity before it enters the high temperature region, since a maximal height of free fall can be chosen. Thus, the time interval during which the material will be exposed to the cracking temperatures of the lower region of the electrode can be decreased to a fraction of a second The hydrocarbon oil that is used according to the invention will usually be a mineral oil, such as a fuel oil or other heavy oil as may be found suitable for the process in question and the pastiness desired.

The method and the hollow electrode of the invention is intended for introducing oil-containing material through a vertical hollow electrode in any electrothermal furnace the process of which lends itself to the use of oil as part of the reducing reactants. The production of calcium carbide from lime and coke, and the production of iron from iron ore and coke are thought to be examples of such processes.

What is claimed is:

1. A method for the introduction of a hydrocarbon oil to the hot zones of a submerged arc reduction furnace through a substantially vertical canal in the electrode comprising intimately premixing said oil with disintegrated solid reactants to be used in the metallurgical process of the furnace, feeding the obtained mixture through a conduit which at least With its lower end protrudes into said vertical canal, the lower end opening of said conduit being substantially smaller than the cross section of said canal and arranged centrally therein, allowing said mixture to fall from the lower end of said conduit to reach the interior of the furnace after a free fall through said canal, and flowing a gas downward through said canal.

2. A method as claimed in claim 1 wherein to said gas flowed downward through said canal there are added substances capable of oxidizing carbonaceous material at high temperatures.

3. A method for the introduction of a hydrocarbon oil to the hot zones of a submerged arc reduction furnace {through a substantially vertical canal in the electrode comprising intimately premixing said oil with disintegrated solid reactants to be used in the metallurgical process of the furnace to obtain a mixture having a paste-like consistency, feeding said mixture through a conduit which at least with its lower end protrudes into said vertical canal, the lower end opening of said conduit being substantially smaller than the cross section of said canal and arranged centrally therein, allowing said mixture to References Cited UNITED STATES PATENTS 2,909,422 10/1959 Schwabe -10 R 3,010,796 11/1961 Alexander 75-10 R 3,078,326 2/1963 Smith 7510 R 3,163,521 12/1964 Rinesch 75-11 3,459,415 10;/ 1969 Hol-czy 75-10 R 1,193,783 8/1916 Hillhouse 75-10 R 1,715,155 5/1929 Westberg 75-11 2,303,973 12/1942 Armstrong 7510 R L. DEWAYNE RUTLEDGE, Primary Examiner P. D. ROSENBERG, Assistant Examiner US. Cl. X.R. 13-l8; 75--10 

